T cell γ gene rearrangements in hematologic neoplasms

Rearrangements of the T cell γ (Tγ) gene were studied in primary neoplastic cells from 75 patients with leukemia or lymphoma. Tγ gene rearrangements were observed in 19 of 21 T cell neoplasms; 14 of 21 immature B cell leukemias, including 4 out of 5 patients with rearrangements of both immunoglobulin heavy-chain (JH) and T cell receptor β chain (β) genes; none out of 14 B cell neoplasms; all 3 unclassified neoplasms; and none out of 16 nonlymphoid leukemias. Thus, Tγ gene rearrangement is frequently found in immature B cells and is not always found in T cells showing Tβ gene rearrangement, but it is not detected in nonlymphoid cells. Furthermore, Tγ gene rearrangement in cells with the germline configuration of the JH and Tβ genes was observed. These results indicate that the detection of Tγ gene rearrangement does not allow a clear assignment to a particular lineage. However, an analysis of Tγ gene rearrangement provides a further potential tool to establish the lymphoid cellular origin and clonality of hematologic neoplasms and identify the normal stages of lymphocyte differentiation.